Your missing out on tactics and a feel for an early initiative
pick up a good book like combinational challenge/ and study classic attacking games from the Anderson and Morphy era that will give you a healthy fear for the initiative and make you well rounded
other than that stay with c4 if you like it
Question for the higher rated players out there. I keep reading from pretty big name GM's things like "Learning to play the open games is vital to a chess players development."
I have largely avoided playing 1. e4, mainly to avoid the major amounts of theory required, and because, well frankly, I am a contrarian. I have been playing 1. c4 mostly.
But I am wondering... am I hurting myself by avoiding a "classical" chess education?